The present invention relates to a drive mechanism for an automotive vehicle seat adjuster and in particular to a floating drive mechanism for a power seat adjuster.
In recent years, automobile designs have changed to a sleeker, more aerodynamic, shape in which the roof line of the vehicle has been lowered. As a result of the lowered roof lines, the occupant seats have changed to a more reclined position in order to comfortably fit the occupant within the vehicle. With the more reclined seats, in order to accommodate various size occupants, the seat adjustment travel in the fore and aft direction has been increased from approximately a five inch travel to a nine to eleven inch travel.
Many power seat adjusters utilize a rack and pinion for moving the seat fore and aft. The seat assembly is attached to a carriage that is slidable along a stationary rack mounted to the vehicle floor pan. The carriage is moved fore and aft by a pinion gear driven by a motor and transmission assembly running on a stationary rack. The machining tolerances of the rack and the carriage can result in an uneven meshing of the pinion gear teeth with the rack teeth over the length of travel of the rack. This creates noise and an uneven or jerky motion during the horizontal seat adjustment. With the five inch seat adjustment travel, the noise and uneven motion is normally within acceptable levels. However, when the rack length is increased to provide a greater horizontal travel, the noise level and uneven motion can exceed acceptable levels.
Accordingly, it is an object of the present invention to provide a drive mechanism that maintains a constant mesh between the pinion gear and the rack along the entire length of travel to avoid noise and uneven motion.
The present invention achieves the objective of maintaining a constant mesh between the pinion gear and rack teeth by providing a floating drive mechanism in which the pinion gear is allowed to move vertically relative to the motor and transmission assembly. The pinion gear is retained in a fixed position relative to the rack so that a constant mesh between the pinion gear and rack teeth is maintained. Flexible couplings in the pinion gear's drive shaft as well as a pivotal connection of the motor and transmission assembly to the carriage enables the motor and transmission assembly and the pinion gear to float relative to one another. A typical seat assembly includes a pair of carriages, racks and pinion gears with one of each disposed along opposite lateral sides of the seat.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.